1. Technical Field
The disclosure relates generally to integrated circuit (IC) chip fabrication, and more particularly, to a phase change material structure and a related method.
2. Background Art
Electronic fuses are used in IC chips, for example, to correct inoperative parts by turning on or off sections. Current electronic fuse (efuse) technology is based on techniques such as electromigration, rupture or agglomeration. These fuse technologies suffer from a number of drawbacks. For example, they are single use, take up large areas, involve quite large amounts of power/current, and are very slow, e.g., microseconds. As fuse technology develops, higher performance is desirable to, for example, reduce area taken up by the fuse, address sun-setting of the non-standard high voltages/currents required (e.g., for electromigration fuses), provide multiple use reprogrammable fuses, and enhance speed.
Phase change material is a type of material capable of resistance changes depending on the mechanical phase of the material. Phase change material is used for phase change memory (PCM), which may also be known as ovonic unified memory (OUM), chalcogenide random access memory (CRAM) or phase-change random access memory (PRAM). Phase change material has not been used for fuse technology.
Almost all PCMs are built using a chalcogenide alloy, typically a mixture of germanium (Ge), antimony (Sb) and tellurium (Te), which is referred to as GST. One GST alloy has the formula: Ge2Sb2Te5. Under high temperature (over 600° C.), a chalcogenide becomes liquid and by subsequent rapid cooling it is frozen into an amorphous glass-like state and its electrical resistance is high. By heating the chalcogenide to a temperature above its crystallization point, but below the melting point, it will transform into a crystalline state with a much lower resistance. In addition, when the material is set to a particular state representing a resistance value, the value is retained until reset by another phase change of the material. The phase switching can be completed very quickly, e.g., under 10 ns. During use as a PCM, the phase of the phase change material is typically changed by heat created by a small pulse of electrical power. Typically, this heat is provided by an internal heater, which presents reproducibility and manufacturing challenges.